Oct/Nov 2017

A purple pill is put into a beaker containing water. The beaker is then left for several hours. The diagram shows how the water looks when the pill is added and again several hours later. Which statement explains the reason for this change?

Diffusion

Chlorine has a relative atomic mass of $35.5$. What mass do 2 moles of chlorine gas have?

The mole and the Avogadro constant

A liquid compound has the empirical formula $\text{C}_2\text{H}_4\text{O}$. In order to determine the empirical formula, it is necessary to know

Formulae

When 25.0 g of hydrated copper(II) sulfate crystals are heated, anhydrous copper(II) sulfate and water vapour are produced. $\text{CuSO}_4\cdot5\text{H}_2\text{O}(s) \rightarrow \text{CuSO}_4(s) + 5\text{H}_2\text{O}(g)$ Determine the mass of anhydrous copper(II) sulfate formed. [$M_r$: $\text{CuSO}_4$, $160$; $\text{H}_2\text{O}$, $18$]

The mole and the Avogadro constant

When one mole of an organic compound, $Q$, undergoes complete combustion in oxygen, exactly three moles of water are formed. Which compound is $Q$?

Formulae, functional groups and terminology

Aluminium is obtained by electrolysing molten aluminium oxide. Which equation correctly represents the reaction taking place at the positive electrode?

Electrolysis

During the electrolysis of aqueous copper(II) sulfate with copper electrodes, which observations are correct?

Electrolysis

Three separate solutions were electrolysed with inert electrodes. solution 1: aqueous sodium chloride solution 2: concentrated hydrochloric acid solution 3: dilute sulfuric acid Which of these solutions gives hydrogen at the negative electrode?

Electrolysis

When conditions are appropriate, nitrogen reacts with oxygen to produce $\text{N}_2\text{O}$. $2\text{N}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{N}_2\text{O}(g)$ The energy profile diagram for this reaction is provided. Determine the activation energy for the reverse reaction.

Rate of reaction

Liquid water can be produced from hydrogen and oxygen in three stages. Which stages absorb heat?

Exothermic and endothermic reactions

Sulfur trioxide is formed in the reaction shown below. $2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g) \qquad \Delta H = -195\ \text{kJ}$ Which change in conditions would result in a larger amount of $\text{SO}_3$ at equilibrium?

Reversible reactions and equilibrium

The outcomes of two tests on solution $X$ are displayed. When aqueous sodium hydroxide is added, a white precipitate forms and then dissolves in excess. When aqueous ammonia is added, a white precipitate forms and does not dissolve. Which ion is present in solution $X$?

Identification of ions and gases

A chemist studied the rate of the reaction between ethene and hydrogen with a nickel catalyst. $\text{C}_2\text{H}_4(g) + \text{H}_2(g) \xrightarrow{\text{Ni}} \text{C}_2\text{H}_6(g)$ Three experiments were done by the chemist using different conditions. Which row is the correct one?

Rate of reaction

Which change takes place every time a metal atom is oxidised?

Redox

Which of the following statements is correct?

Elements, compounds and mixtures

Which reagent can be used to react with dilute hydrochloric acid so as to produce silver chloride?

Preparation of salts

The table lists some symbols and what they represent. Which symbols should be included in the equation for the Haber process?

Reversible reactions and equilibrium

Nitrogenous fertilisers may lead to eutrophication in rivers. The stages of eutrophication are given below. 1 The fertiliser is washed into the river. 2 Oxygen levels become depleted in the river. 3 Plants die. 4 Plants begin to decay. 5 Plants in the river grow at an increased rate. What is the correct sequence of these five stages in eutrophication?

Fertilisers

Three possible applications of sulfuric acid are given.

The characteristic properties of acids and bases

One atom of element Q contains 17 electrons in total, and one atom of element R contains 19 electrons in total. Which statement about elements Q and R is correct?

Atomic structure and the Periodic Table

Which row gives the right catalyst for each industrial process?

Rate of reaction

Which metal is fixed to underground iron pipes to give sacrificial protection against corrosion?

Corrosion of metals

Which diagram represents how the particles are arranged inside a balloon that contains a mixture of the gases nitrogen and oxygen?

Solids, liquids and gases

The diagram illustrates a circuit designed to check the electrical conductivity of strips made from solid substances. When the substance conducts, the bulb comes on. Separate strips of brass, nylon and zinc are each joined to the circuit one at a time. For which strips will the bulb come on?

Properties of metals

Octane, $\text{C}_8\text{H}_{18}$, is a hydrocarbon that burns by combustion in a petrol engine. $\ldots w\,\text{C}_8\text{H}_{18} + \ldots x\,\text{O}_2 \rightarrow \ldots y\,\text{CO}_2 + \ldots z\,\text{H}_2\text{O}$ Which row contains the numbers required to balance the equation?

Formulae

The diagram illustrates a section of the carbon cycle. What are processes P, Q and R?

Air quality and climate

CFC compounds have been used as aerosol propellants. The structure of one CFC compound is shown. Which element in this compound is responsible for ozone depletion in the atmosphere?

Air quality and climate

What gets removed or destroyed when water is desalinated so that it becomes safe to drink?

Water

Compounds S and T each consist of only two elements. They show the following characteristics. • When burned in air, both produce only carbon dioxide and water. • Both undergo substitution with chlorine. • The boiling point of S is higher than that of T. What might compounds S and T be?

Alkanes

Which row gives the correct description of alkenes?

Alkenes

The table lists statements about the ways ethanol is manufactured on a large scale from ethene and from glucose. Which rows are correct?

Alcohols

The ester’s structure is shown. What is this ester called?

Naming organic compounds

Which compound gives an aqueous solution with a pH below $7$?

The characteristic properties of acids and bases

A student tracks the rate of reaction between marble chips, $\text{CaCO}_3$, and dilute hydrochloric acid. $\text{CaCO}_3 + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{CO}_2 + \text{H}_2\text{O}$ Which diagrams show apparatus that is appropriate for this experiment?

Rate of reaction

The diagram represents the repeat unit of a polymer. Which row correctly identifies the monomer and the type of polymerisation used to make this polymer?

Polymers

Equal masses of methane gas are kept under different conditions. At which set of conditions will the methane gas take up the smallest volume?

Solids, liquids and gases

A particle of a sulfur isotope has 18 neutrons and 18 electrons. What is its symbol?

Isotopes

When two elements react with one another, a compound is produced. Which statement is correct?

Elements, compounds and mixtures

Which of the following statements is true for every ionic compound?

Ion and ionic bonds

When a sample of sodium is heated in air, it reacts with oxygen to produce the ionic compound sodium oxide, $\text{Na}_2\text{O}$. In terms of electrons, which statement correctly describes what occurs when sodium reacts with oxygen?

Ion and ionic bonds

A mixture containing sand and sodium chloride can be separated in three stages. In step 1, water is added to the mixture. The diagram illustrates steps 2 and 3. At which point is pure sodium chloride collected?

Separation and purification

$25.0\,\text{g}$ of hydrated copper(II) sulfate crystals are heated so that anhydrous copper(II) sulfate and water vapour are produced. $\text{CuSO}_4\cdot5\text{H}_2\text{O(s)} \rightarrow \text{CuSO}_4\text{(s)} + 5\text{H}_2\text{O(g)}$ Calculate the mass of anhydrous copper(II) sulfate made. $[M_r: \text{CuSO}_4 = 160; \text{H}_2\text{O} = 18]$

Relative masses of atoms and molecules

Which sample contains the greatest number of atoms?

The mole and the Avogadro constant

The relative atomic mass for chlorine is $35.5$. Calculate the mass of $2$ moles of chlorine gas.

The mole and the Avogadro constant

When one mole of the organic compound Q is completely burnt in oxygen, exactly three moles of water are formed. Which compound is Q?

Formulae, functional groups and terminology

In one experiment, $1$ mol of powdered copper and $1$ mol of powdered zinc are put into a flask. Dilute acid, with $1$ mol of acid in it, is then added to the flask. The flask is then kept until any reactions that occur have finished. Which diagram shows the outcome of the experiment?

Reactivity series

A simple cell may be constructed by using two different metals as the electrodes together with an aqueous solution as the electrolyte. Which statements about simple cells are correct?

Electrolysis

Magnesium may be obtained by electrolysing molten magnesium chloride, $\text{MgCl}_2$. What are the equations for the reactions taking place at the positive electrode and at the negative electrode?

Electrolysis

Three separate solutions were electrolysed by using inert electrodes. solution 1: aqueous sodium chloride solution 2: concentrated hydrochloric acid solution 3: dilute sulfuric acid Which of the solutions gives hydrogen at the negative electrode?

Electrolysis

Compound Y undergoes a reaction with oxygen. This reaction shows a positive enthalpy change of reaction, $\Delta H$. What can be inferred about Y and its reaction with oxygen?

Exothermic and endothermic reactions

The conversion of hydrogen and oxygen into liquid water can take place in three stages.

Exothermic and endothermic reactions

The outcomes of two tests carried out on solution $X$ are shown below. Aqueous sodium hydroxide: a white precipitate is formed, and the precipitate dissolves in excess. Aqueous ammonia: a white precipitate is formed, and the precipitate does not dissolve. Which ion is present in solution $X$?

Identification of ions and gases

Sulfur trioxide is formed by the reaction shown here. $2\text{SO}_2\text{(g)} + \text{O}_2\text{(g)} \rightleftharpoons 2\text{SO}_3\text{(g)} \quad \Delta H = -195\,\text{kJ}$ Which change in conditions would give a larger amount of $\text{SO}_3$ at equilibrium?

Reversible reactions and equilibrium

Magnesium undergoes reaction with dilute sulfuric acid. $\text{Mg(s)} + \text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{MgSO}_4\text{(aq)} + \text{H}_2\text{(g)}$ There were two separate experiments. In experiment 1, $24.0\,\text{g}$ of magnesium was reacted with $100\,\text{cm}^3$ of $1.0\,\text{mol dm}^{-3}$ sulfuric acid. In experiment 2, $24.0\,\text{g}$ of magnesium was reacted with $50\,\text{cm}^3$ of $2.0\,\text{mol dm}^{-3}$ sulfuric acid. For each experiment, the hydrogen volume was recorded at different times. The data were then plotted on a graph. Which graph is the correct one?

Rate of reaction

Which statement applies to both aluminium and iron?

Properties of metals

A domestic cleaning compound is applied to take off calcium carbonate from bathroom surfaces. The compound reacts with the calcium carbonate to produce a soluble salt, carbon dioxide and water. What is the pH of this cleaning compound?

The characteristic properties of acids and bases

Separate samples of copper, copper(II) oxide and copper(II) carbonate are each treated with dilute hydrochloric acid. Which row correctly indicates whether copper(II) chloride is formed?

The characteristic properties of acids and bases

Which ions are present when hydrochloric acid has just neutralised aqueous sodium hydroxide?

The characteristic properties of acids and bases

Which experiment will produce a white precipitate?

Identification of ions and gases

Which statement about both the Group I and Group VII elements is true?

Arrangement of elements

Helium, argon and neon are noble gases. Which statement is correct?

Noble gases

Which row gives the correct catalyst for each industrial process?

Rate of reaction

Which diagram represents how the particles are arranged inside a balloon that contains a mixture of nitrogen and oxygen gases?

Solids, liquids and gases

In the solid state, germanium has the same structure as diamond. State the likely melting point of germanium.

Giant covalent structures

Aluminium is a metal that is commonly used to produce bottle caps. If these caps are discarded and placed in soil, they do not corrode. What is the reason for this?

Corrosion of metals

Which of the following statements about Group I metals is true?

Group I properties

CFC compounds were once used as aerosol propellants. The formula of one CFC compound is shown. Which element in this compound leads to depletion of ozone in the atmosphere?

Air quality and climate

Dry air consists of a mixture of gases, and $99\%$ of it is nitrogen and oxygen. What is the principal component of the remaining $1\%$?

Elements, compounds and mixtures

What is the purpose of adding chlorine to the water supply?

Water

When an alcohol with molecular formula $\text{C}_4\text{H}_{10}\text{O}$ undergoes oxidation, what is the molecular formula of the acid produced?

Alcohols

The diagrams illustrate the structures of five hydrocarbons. Which three hydrocarbons are isomers of one another?

Alkanes

Which alcohol and which acid react with one another to form the ester $\text{CH}_3\text{COO}\text{C}_2\text{H}_5$?

Carboxylic acids

Which compound gives an aqueous solution with a pH below 7?

The characteristic properties of acids and bases

A student monitors the rate of reaction between marble chips, $\text{CaCO}_{3}$, and dilute hydrochloric acid. $\text{CaCO}_{3} + 2\text{HCl} \rightarrow \text{CaCl}_{2} + \text{CO}_{2} + \text{H}_{2}\text{O}$ Which diagrams show apparatus that is appropriate for this experiment?

Rate of reaction

Which of the following statements about polymers is correct?

Polymers

A chemist wants to separate and identify a mixture of substances by using paper chromatography. The diagram shows the apparatus used. The solvent is water. The chemist leaves the solvent front to reach the top of the paper before removing the paper from the solvent. What problem does this lead to?

Chromatography

Which particle has an equal number of neutrons and electrons?

Atomic structure and the Periodic Table

Which statement is true for every metal?

Properties of metals

X is the element with atomic number 8, and Y is the element with atomic number 19. These two elements combine to make a compound. Which row gives the correct information for the compound produced?

Ion and ionic bonds

The empirical formula of a liquid compound is $\text{C}_2\text{H}_4\text{O}$. In order to determine the empirical formula, it is necessary to know

Formulae

Use the elements listed below to answer the questions. calcium chlorine chromium copper krypton nitrogen oxygen sodium sulfur You may use any element once, more than once, or not use it at all.

Atomic structure and the Periodic Table

Copper(II) sulfate is classified as an ionic compound.

Electrolysis

The illustration shows how the atoms are arranged in a metal.

Extraction of metals

The structure of malic acid is displayed.

Polymers

When hydrocarbons burn completely, they produce carbon dioxide and water.

Alkanes

Ethanoic acid counts as a weak acid.

Carboxylic acids

The table lists some properties of the Group IV elements.

Arrangement of elements

Concentrated aqueous ammonia is used in the manufacture of fertilisers such as ammonium phosphate, $(\text{NH}_4)_3\text{PO}_4$.

Fertilisers

Cyclopropane changes into propene when heated.

Alkenes

Use the elements listed below to answer the questions. aluminium carbon hydrogen iron magnesium nitrogen oxygen sodium vanadium Each element can be selected once, more than once, or left unused.

Atomic structure and the Periodic Table

NaCl, sodium chloride, and magnesium chloride, MgCl$_2$, are both ionic compounds.

Electrolysis

Metals are recognised by physical properties like good electrical and thermal conductivity.

Properties of metals

Lavandulol occurs in lavender plants.

Formulae, functional groups and terminology

When dilute ethanoic acid reacts with sodium carbonate, sodium ethanoate, CH$_3$COONa, together with two further compounds, is produced.

Preparation of salts

When the temperature is high, hydrogen combines with iodine to produce hydrogen iodide. $\text{H}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{HI}(g) \qquad \Delta H = +53.0\ \text{kJ mol}^{-1}$

Reversible reactions and equilibrium

The table lists the melting points and relative electrical conductivities of three elements in Period 3 of the Periodic Table.

Giant covalent structures

Fertilisers contain potassium nitrate, potassium sulfate and potassium phosphate.

Fertilisers

When heated, nitrogen(V) oxide breaks down to make nitrogen(IV) oxide and oxygen. $2\text{N}_2\text{O}_5(g) \rightarrow 4\text{NO}_2(g) + \text{O}_2(g)$

Rate of reaction

The diagrammed apparatus is used for the electrolysis of dilute hydrochloric acid.

Electrolysis

Fullerenes are solid carbon allotropes. They are present in soot, which also contains other carbon allotropes. Fullerenes dissolve in liquid hydrocarbons such as heptane, whereas the other carbon forms in soot do not dissolve in heptane.

Separation and purification

The apparatus shown can be used to oxidise ethanol to ethanoic acid with acidified aqueous potassium manganate(VII). The diagram contains mistakes.

Experimental design

A learner receives a contaminated sample of magnesium carbonate, $\text{MgCO}_3$. The learner works out what percentage of the sample’s mass is magnesium carbonate.

Acid–base titrations

The table below lists the tests that a student carries out on compound L.

Identification of ions and gases

At room temperature, aqueous hydrogen peroxide breaks down in the presence of a catalyst to make water and oxygen. $2\text{H}_2\text{O}_2(\text{aq}) \rightarrow 2\text{H}_2\text{O}(\ell) + \text{O}_2(\text{g})$.

Rate of reaction

A student performs experiments with two different electrolytes in the apparatus illustrated.

Electrolysis

Ethanol acts as a reducing agent. If it is warmed with acidified aqueous potassium manganate(VII), it can be oxidised. It also evaporates readily at room temperature. As a solvent, it can be used to separate the dyes found in ink. A student uses the apparatus illustrated to perform the separation. The diagram contains errors.

Chromatography

A student examines how rapidly four metal carbonates break down. When metal carbonates are heated, they decompose and release a gas. The student proposes judging how readily different carbonates decompose by timing how long a sample of limewater takes to become milky, using the apparatus shown. The results of the investigation are shown in the table.

Rate of reaction

A student receives an impure sample of calcium hydroxide, $\text{Ca(OH)}_2$. The student wants to find the percentage by mass of calcium hydroxide in the sample.

Acid–base titrations

The table below lists the tests that a student carries out on compound $L$.

Identification of ions and gases

When alcohols burn in air, heat energy is released to the surroundings. A student is investigating how much heat energy is produced when alcohols burn.

Exothermic and endothermic reactions